1. Field of the Invention
The present invention relates to patient motion monitoring systems used in medical radiation facilities, and in particular, patient motion monitoring systems that are adapted to prevent a collimated beam of particles from reaching a patient whenever the patient moves more than a threshold level.
2. Description of the Related Art
Energetic particle beams are sometimes used by medical practitioners to treat cancerous regions in patients. In particular, when a particle beam is directed at a cancerous tumor within a patient, the penetrating nature of the particle beam allows the beam to reach a deep seated tumor and deposit energy within the tumor. As energy is absorbed by the tumor, the DNA structures within the cells of the tumor are altered. If enough energy is absorbed by the tumor, it is possible to cause irreparable damage to the DNA structures, thus causing the tumor to diminish in size or even die completely.
A particularly effective form of particle beam therapy involves the use of energetic protons. In particular, proton therapy centers, such as the Loma Linda Proton Facility at Loma Linda University in Loma Linda. Calif., are capable of producing a proton beam having a per particle energy up to 256 MeV. Protons within this energy range are able to penetrate deeply into the human body in a substantially straight path and deposit the majority of their energy in a localized region of the body. In particular, if the energy of a proton is sufficiently above a threshold value, known as the xe2x80x9cBragg peakxe2x80x9d, then the proton loses kinetic energy at a moderate rate as it passes through matter. However, when the kinetic energy of the proton is reduced to the Bragg peak threshold, the remaining kinetic energy of the proton is rapidly released. Therefore, a proton beam can be configured to release the majority of its energy within a tumor of a patient by adjusting the energy of the proton beam according to the amount of cellular material that is situated in front of the tumor so that the proton energy is reduced to the Bragg peak as the proton reaches the tumor.
However, given the relatively high radiobiologic effects of particle beams, such as proton beams, it is often desirable to limit patient movement during treatment so that movement of the patient will not result in the beam being misdirected and affecting healthy tissue within the patient""s body. To prevent misalignment between the proton beam and the tumor in proton therapy, stereotactic fixation systems such as those described in U.S. Pat. Nos. 5,797,924, 5,549,616, and 5,464,411 have been developed and are often used in the treatment process. In particular, these immobilization devices are designed to limit the range of motion of the patient to within a fixed tolerance which is suitable for treating comparatively large tumors.
However, as treatment of smaller tumors located in more sensitive regions has become more desirable, an increasing need has developed for systems capable of preventing excessive misalignment. For example, a new field of proton therapy is being investigated which focuses on small intracranial tumors and functional disorders of the brain. In these cases the proton beam is required to align with relatively small intracranial targets with diameters between 1 cm and 3 cm. Given that tumors are surrounded by brain tissue misalignment of the beam in this environment can be very harmful to the patient. Consequently, correct patient alignment within 1 mm is an indispensable requirement for these treatments.
In research studies performed by the Applicants, the movement of patients receiving proton beam therapy while utilizing prior art stereotactic fixation immobilization devices was monitored. In particular, the results of these studies indicate that patient movement by as much as several mm. Furthermore, these studies indicate that patient motion is often oscillatory in nature with an average patient position that is within 1 mm of the ideal position and a period that often correlates to respiratory activity. Therefore, it is apparent from these results that the use of immobilization devices known in the art are not sufficient to provide optimal treatment of small intracranial targets with diameters between 1 cm and 3 cm.
From the foregoing, it will be appreciated that there is a need for a patient monitoring system that operates in conjunction with a proton beam facility that is capable of detecting movement of a patient by as little as 1 mm in any direction furthermore, this system should be capable of disabling the proton beam whenever unacceptable motion of the patient is detected. Preferably, the device should have a fast response time so as to exploit the oscillatory nature of patient motion. In particular, if the motion is attributed to inhalation and exhalation processes, the patient monitoring system should have a response time that is significantly shorter than the breathing period so as to allow the patient to receive safe and effective proton therapy during times of proper alignment between the proton beam and the intended target.
There is also a need for such a devise that is easily adaptable for use in presently available proton beam facilities. For example, it would be advantageous for a medical practitioner to be able to easily move the device from one treatment room to another, quickly mount the device to any available solid structure, and easily and effectively position the device so as to monitor the movement of a patient. Furthermore, the device should be non-invasive to the patient and also provide feedback to the practitioner so as to allow the practitioner to modify the treatment procedure for maximum effectiveness. Moreover, the device should operate reliably and be relatively inexpensive to produce.
The aforementioned needs are satisfied by the present invention which in one aspect is comprised of a patient motion monitoring system for use with a particle beam therapy system. In this aspect, the system comprises a first energy source adapted to direct a beam towards a surface of the patient substantially positioned in a desired orientation and a first sensor that receive a reflected beam from the first energy source that is reflecting off of the surface of the patient wherein the sensor provides a first signal indicative thereof. The system further comprises at least one positioning mechanism that allows for the first energy source and the first sensor to be positioned a selected distance from the surface of the patient and a controller that receives the first signal from the first sensor and determines the location of the patient based upon the first signal from the sensor, wherein the controller evaluates the first signal to determine if the patient has moved more than a selected threshold amount from the desired orientation.
In another aspect the present invention is comprised of a patient motion monitoring system for use with a particle beam therapy system. In this aspect, the monitoring system comprises a first non-contact sensor that shines a first signal against a surface of a patient substantially positioned in a desired orientation and obtains a reflected signal, wherein the first non-contact sensor provides a first output signal indicative of the received reflected signal and a second non-contact sensor that shines a second signal against a surface of the patient and obtains a reflected signal, wherein the second non-contact sensor provides a second output signal indicative of the received reflected signal. The system also comprises a controller that receives the first and second output signal, wherein the controller uses the first and second output signals to evaluate whether the patient has moved more than a selected threshold amount from the desired orientation and provides a patient movement signal indicative thereof upon determining that the patient has moved more than the selected threshold amount.
In yet another aspect, the present invention is comprised of a particle beam delivery system. The particle beam system comprises a particle beam delivery system for delivering a therapeutic particle beam to a specific location within a patient. The particle beam delivery system further comprises a non-contact patient motion monitoring system, the non-contact patient motion monitoring system having a first non-contact sensor that directs a beam towards a surface of the patient substantially positioned in a desired orientation and receives a reflected beam therefrom, wherein the first non-contact sensor provides a first output signal indicative of the distance of the patient from the first non-contact sensor and wherein the non-contact patient motion monitoring system further includes a controller that receives the first output signal and evaluates the first output signal to determine if the patient has moved more than a selected threshold amount from the desired orientation and wherein the controller provides a patient movement signal adapted to allow for interruption of delivery of the therapeutic particle beam upon determining that the patient has moved more than the selected threshold amount from the desired orientation.
In yet another aspect, the present invention comprises a method of monitoring the motion of a patient. In this aspect, the method comprises directing a first non-contact beam from a first location towards a surface of a patient position substantially in a desired orientation; receiving a reflected beam from the surface of the patient as a result of directing the first non-contact beam towards the surface of the patient; evaluating the reflected beam to determine a distance value that corresponds to the distance of the patient from the first location; determining whether the distance value indicates that the patient has moved more than a selected threshold amount from the desired orientation; and providing a signal indicating that the patient has moved more than the desired threshold amount.
From the foregoing, it will be appreciated that the non contact monitoring system and method of the present invention provides a non-contact system for determining whether the patient has moved from a desired orientation to thereby either provide a warning or inhibit the delivery of therapeutic particle beams. These and other objects and advantages of the present invention will become more fully apparent from the following description taken in conjunction with the accompanying drawings.